Cylinder motor apparatus

Abstract: A cylinder motor apparatus includes a chassis, a shaft, a circuit board, a supporting member for supporting the shaft on the chassis in a freely rotatable state, a rotor fixed to the shaft, which has a stator housing defined into an annular depression shape opened in the direction opposite to the supporting member and a magnet provided in the stator housing, a stator housed in the stator housing and fixed to the circuit board, and an electric circuit provided on the circuit board for controlling the rotation of the rotor.

Description: The present invention generally relates to a cylinder motor apparatus which rotates a rotating member by utilizing a rotor and a stator, and also to a magnetic recording or reproducing apparatus utilizing the cylinder motor apparatus. In recent years, magnetic recording or reproducing apparatus,such as video tape recorders, digital audio tape recorders, for recording on or reproducing from magnetic tapes through rotary heads have rapidly come into wide use in home. To address demands for low-profile equipment, some of these devices have a cylinder motor apparatus to rotate a rotor mounted to the rotary head shaft of the cylinder by a fixed stator core assembly. FIGURE 1 shows a cross-sectional view illustrating a known cylinder motor apparatus and its peripheral members. In FIGURE 1, reference numeral 51 denotes a chassis. On the chassis 51, there is defined a hole 52 into which a cylinder motor apparatus 61 is inserted. On one side of the chassis 51, a cylinder 54 is mounted by a fastener 53 at a predetermined angle. A through-hole 55 is defined through the center of the cylinder 54. A shaft 56 with a rotary head mounted on its one end is inserted into the through-hole 55 from one end of the cylinder 54. A ball bearing 57 is provided between the inner surface of the through-hole 55 and the shaft 56 so that the shaft 56 is able to rotate against the cylinder 54 at a low load condition. There is a step 58 provided at the end of the cylinder 54. The outer cylindrical wall of the step 58 is fittedto a central opening of a cylinder-contained circuit board 62, while the flat surface of the step 58 is contact with the one side of a cylinder-contained circuit board 62 at a portion around the central opening. There is a stator core assembly 64 provided on the other side of the cylinder-contained circuit board 62 via a spacer 63. The stator core assembly 64, the spacer 63 and the cylinder-contained circuit board 62 are fixed around the step 58 of the cylinder 54 by screws 65. A coil 66 is wound around the stator core assembly 64. At the end of the shaft 56, a rotor 67 is mounted. The rotor 67 is provided on its one side with an edge 68 which encircles the stator core assembly 64. A magnet 69 is mounted on a predetermined position of the edge 68. The magnet 69 has such a shape that a notch 70 fits to the edge 68 so that a magnetic field is generated over the inside and the outside of the edge 68. A circular fastener 71 is provided around the shaft 56 on one side of the rotor 67 to stably hold the rotor 67 against the shaft 56. A rotation detecting sensor 72 is provided on the other side of the cylinder-contained circuit board 62. The rotation detecting sensor 72 detects the rotation of the rotor 67 by detecting the magnetic field generated by the magnet 69. The cylinder motor apparatus 61 is thus constituted by such a structural arrangement of the cylinder-contained circuit board 62, the spacer 63, the stator core assembly 64, the screw 65, the coil 66, the rotor 67, the magnet 69, the circular fastener 71 and the rotation detecting sensor 72, as described above. There is a main circuit board 81 provided, in a spaced apart manner a predetermined distance from the other side of the chassis 51. The main circuit board 81 defines an opening 82 into which the rotor 67 and the shaft 56 are to be inserted. A connector 73 is provided at the corner of the other side of the cylinder-contained circuit board 62. Also, another connector 83 is provided beside the opening 82 on the main circuit board 81. The connector 83 is then electrically connected to the connector 73 through a lead 84. In such a conventional cylinder motor apparatus when the shaft 56 is rotated as described above, a power supply voltage applied to the main circuit board 81 is led to the cylinder-contained circuit board 62 through the lead 84. Thus, a current is supplied to the coil 66 and thus a rotating magnetic field is applied to the magnet 69 to generate a rotating force for rotating the rotor 67 and the shaft 56. The rotation of the rotor 67 is detected by the rotation detecting sensor 72. A detected signal resulted by the detection of the rotation of the rotor 67 is fed back to the main circuit board 81 through a lead 84. The main circuit board 81 regulates the power supply voltage applied thereto, based on the detection signal, to keep the rotation of the rotor 67 constant. According to such a conventional cylinder motor apparatus, since it is necessary to provide the cylinder-contained circuit board 62 in addition to the main circuit board 81 and in order to fasten the cylinder-contained circuit board 62 to the cylinder 54 by a screw, manufacturing processes and parts count increase. And furthermore connectors and leads will be also needed to electrically connect the main circuit board 81 and the cylinder-contained circuit board 62 and also operations for connecting these circuit components will be needed. As a result, it is difficult to reduce the manufacturing cost. In the conventional cylinder motor apparatus, it is difficult to reduce the manufacturing cost, due to the fastening of the cylinder-contained circuit board and the electrical connection between the main circuit board and the cylinder-contained circuit board, as the cylinder-contained circuit board is provided in addition to the main circuit board. In addition, as the stator is mounted between the rotating member and the rotor, the stator and the main circuit board have to be individually mounted to the rotating member, and it is further made difficult to reduce the manufacturing cost. Furthermore, as the air hardly circulates between the rotor and the stator in a state of high atmospheric temperature in the summer season, for example, the motor is heated excessively by the current flowing in the stator coil, thus causing defective operations or troubles in some cases. The present invention therefore seeks to provide a cylinder motor apparatus which is capable of rotating a rotor without providing a circuit board in a cylinder. The present invention also seeks to provide a cylinder motor apparatus which is capable of mounting both the stator and the main circuit board at one time on the rotating member. Furthermore, the present invention seeks to provide a cylinder motor apparatus which has improved air circulation between the rotor and the stator. Yet further, the present invention provides a magnetic recording or reproducing apparatus which utilizes such a cylinder motor apparatus as described above. WO 91/06954 discloses a cylinder motor as defined in the preamble of claim 1. The stator is mounted on a separate printed circuit board being mounted transversely to the axis and connected with bendable connectors to the circuit board carrying the motor control circuits. JP-A-62 047 896 discloses the use of holes and vanes in a cylinder motor for cooling purposes JP-A-63 186 550 discloses a cylinder motor wherein the stator coils are connected to a printed circuit board being traverse to the motor axis. According to the present invention, there is provided a cylinder motor apparatus as defined in claim 1 comprising: a chassis; a shaft; a main circuit board fixed relative to the chassis and having an electric circuit provided thereon to control the rotation of a rotor; a supporting member for supporting the shaft on the chassis in a freely rotatable state; a rotor rotatable with the shaft, which rotor has a stator housing defined therein and a magnet provided in the stator housing; and a stator housed in the stator housing, characterised in that the stator housing opens in a direction opposite from the supporting member; and the stator is mounted on the circuit board. According to the structure of the claimed cylinder motor apparatus the rotor can be rotated without providing a circuit board in the cylinder, as the stator is mounted on the main circuit board. Advantageously the stator housing is annular and has inner and outer coaxial circular walls. Preferably holes are provided at the crown of the stator housing. Thus the air circulation between the rotor and the stator can be improved as the through-holes are formed on the crown of the rotor. Additional objects and advantages of the present invention will be apparent to persons skilled in the art from a study of the following description and the accompanying drawings. For a better understanding of the present invention and to show how it may be brought into effect, reference will now be made, by way of example, to the accompanying drawings, wherein: FIGURE 1 is a cross-sectional view showing a conventional cylinder motor apparatus. FIGURE 2 is a cross-sectional view showing one embodiment of a motor apparatus according to the present invention; FIGURE 3 is a perspective bottom view of the chassis of FIGURE 2; FIGURE 4 is an exploded perspective view of a video tape recorder which utilizes the motor apparatus shown in FIGURE 2; FIGURE 5 is a cross-sectional view showing another embodiment of the motor apparatus according to the present invention; FIGURE 6 is a plan view showing the rotor of FIGURE 5; FIGURE 7 is a cross-sectional view showing still another embodiment of the motor apparatus according to the present invention; FIGURE 8 is a plan view showing the rotor of FIGURE 7; and FIGURE 9 is a partial cross-sectional view of the rotor at the line B-B in FIGURE 8. The present invention will be described in detail with reference to FIGURES 2 through 9. Throughout the drawings, reference numerals or letters in FIGURE 1 will be used to designate like or equivalent elements for simplicity of explanation. Referring now to FIGURE 2, a first embodiment of the cylinder motor apparatus according to the present invention will be described in detail. FIGURE 2 is a cross-sectional view for illustrating the first embodiment of the cylinder motor apparatus according to the present invention. In FIGURE 2, reference numeral 11 denotes a chassis. On the chassis 11, an opening 12 is defined for receiving therein a motor apparatus 21. A cylinder 14 is mounted on one side of the chassis 11 by a fastener 13 at a predetermined angle. At the center of the cylinder 14, a through-hole 15 is defined. A shaft 16 having mounted on its one end a rotary cylinder (not shown) having a magnetic head is inserted into the through-hole 15 from one end of the cylinder 14. Between the inner surface of the through-hole 15 and the shaft 16, a ball bearing 17 is provided. Thus the shaft 16 is rotatable in the cylinder 14 at low load condition. There is also defined a step 18 at the other end of the cylinder 14. The main circuit board 31 defines an opening 32 into which both the inner portion of the rotor 24 and the shaft 16 are inserted, while another opening 33 into which the outer portion of the rotor 24 is inserted is also defined on the main circuit board 31. On one side of the main circuit board 31, a stator core assembly 22 is provided at the same angle as the cylinder 14. The stator core assembly 22 has a structure that plural cores 22b are laminated in one body on one end of a cylindrical member 22a along the axis of the cylindrical member 22a. The other end of the cylindrical member 22a is partially cut out at a bevel for its axis, while legs 22c, extending axially for mounting thereto the main circuit board 31, remain on the other end of the cylindrical member 22a. The legs 22c have different length and some of the legs 22c are vertically aligned to the main circuit board 31. The stator core 22 is mounted to the main circuit board 31 at the same angle as the cylinder 14 by fixing the legs 22c to the main circuit board 31 so that the other end of the cylindrical member 22a is fitted to one side of the main circuit board 31. Further, a coil 23 is wound around the core 22b of the stator core assembly 22 and a plurality of lead terminals 22e for the coil 23 are provided to the cylindrical member 22a to project in the same direction as the circuit board mounting legs 22c. The terminals 22e are inserted into inserting holes of the main circuit board 31 in the assembling process of the stator core assembly 22 to the main circuit board 31 so that the coil 23 and the main circuit board 31 are electrically connected each other. At the other end of the shaft 16, the rotor 24 is mounted. The rotor 24 which is molded from a thermoplastic material, has a depression 25 defined on it at one end, which depression 25 fits with the step 18, and an annular depression 26, which receives therein the stator core assembly 22, is defined on its other end. A circular magnet 27 is mounted in the annular depression 26 at a predetermined position facing the stator core assembly 22. The circular magnet 27 generates a magnetic field in the annular depression 26. As the rotor 24 is so arranged that its central portion is laid inside the cylindrical member of the stator core assembly 22. Further the inner wall of the depression 25 of the rotor 24 is provided with a projection 30 which extends in the axial direction from the end of the inner wall. When assembling the main circuit board 31 with the stator core assembly 22 mounted to position the stator core assembly 22 in the depression 25 of the rotor 24, the projection 30 is first brought in contact with the cylindrical inner wall which acts as a guide in the inserting and assembling processes. A circular supporter 28 is fitted to the shaft 16 within the depression 25 of the rotor 24. The rotor 24 is stably secured to the circular supporter 28 by a screw 24a so that the rotor 24 rotates in conjunction with the shaft 16. At the position close to the circular magnet 27 on the one side of the main circuit board 31, a rotation detecting sensor 29 is provided. The rotation detecting sensor 29 detects the rotation of the rotor 24 by detecting the magnetic field generated by the circular magnet 27. The cylinder motor apparatus 21 is constituted in the structure as described above by the stator core assembly 22, the coil 23, the rotor 24, the magnet 27, the circular supporter 28 and the rotation detecting sensor 29. In order to rotate the shaft 16 of the cylinder motor apparatus 21 embodied as described above, the main circuit board 31 applies a voltage to the coil 23 to supply a current thereto. Thus a rotating magnetic field is applied to the magnet 27, and in turn a rotating force for the rotor 24 and the shaft 16 is generated. The rotation of the rotor 24 is detected by the rotation detecting sensor 29 and then the detected signal is fed back to the main circuit board 31. The main circuit board 31 adjusts the current flowing through the coil 23 by regulating the voltage applied to the coil 23 in order to keep the rotation of the rotor 24 constant. The main circuit board 31 is equipped with such circuit components constituting an electric circuit including a recording or reproducing circuit, servo circuits, control circuits, etc., for video tape recorders in which the cylinder motor apparatus according to the present invention is mounted, and is mounted to the chassis 11. According to the first embodiment of the present invention, the cylinder motor apparatus is able to rotate the rotor without providing a circuit board in the cylinder, thus the manufacturing cost of the cylinder motor apparatus is reduced. FIGURE 3 shows a perspective bottom view for illustrating the entirety of the chassis 11. On the bottom surface of the chassis 11, the rotor 24 is mounted in facing its circular depression 26 to the stator core assembly 22. Further, catches 101, 102, 103 and 104 are provided around four corners of the bottom surface of the chassis 11. At the lower left of the front of the chassis 11, a positioning projection 105 is provided. On the lower left and right of the back of the chassis 11, positioning projections 106 and 107 are provided. In addition, a screw clamping part 108 is provided on the side of the rotor 24. FIGURE 4 is a exploded perspective view of a video tape recorder which utilizes the cylinder motor apparatus as shown in FIGURE 2. On the main circuit board 31, the opening 32 as shown in FIGURE 2 as well as the opening 33 are defined. On the surface facing to the chassis 11 of the main circuit board 31, the stator core assembly 22 is provided at the same angle as the cylinder 14. Further, on the main circuit board 31, there are defined through-holes 111, 112, 113 and 114 in which the catches 101, 102, 103 and 104 are caught, a positioning notch 115 into which the positioning projection 105 is inserted and positioning through-holes 116 and 117 into which positioning projections 106 and 107 (see FIGURE 3) are inserted. Further, a through-hole 118 through which a screw 110 is inserted into a screw clamping part 108 is defined on the main circuit board 31. When assembling these chassis 11 and the main circuit board 31, they are combined together by inserting the positioning projection 105 into the positioning notch 115 and the positioning projections 106 and 107 into the positioning through-holes 116 and 117, respectively. Thus, the stator core assembly 22 is inserted into the circular depression 26 of the rotor 24 and at the same time, the catches 101, 102, 103 and 104 are inserted into and caught by the through-holes 111, 112, 113 and 114. Thereafter, the chassis 11 and the main circuit board 31 are completely fixed by inserting the screw 110 into the through-hole 118 and screwing into the screw clamping part 108. By combining the chassis 11 and the main circuit board 31 together as described above, it becomes possible to mount the stator core assembly 22 and the main circuit board 31 collectively at a time on the cylinder 14 and to reduce the manufacturing cost by simplifying the manufacturing processes. FIGURE 5 shows a cross-sectional view for illustrating another embodiment of the motor apparatus according to the present invention. In the embodiment of FIGURE 5, the same components as the embodiment shown in FIGURE 2 are assigned the same reference numerals, and a detailed description of those parts has been omitted. On the crown of the annular depression 126 of a rotor 124, through-holes 131 are formed to circulate air in the space between the rotor 124 and the stator core assembly 22 to the outside. In FIGURE 6 the circular magnet 127 is represented by three coaxial broken lines. FIGURE 6 shows a plan view for illustrating the rotor 124 shown in FIGURE 5. On the crown of the annular depression 126 of the rotor 124, eight through-holes 131 are formed along the circumferential direction. According to the embodiment, the same effects as in the embodiment shown in FIGURE 2 are obtained, and furthermore air circulates between the rotor 124 and the stator core assembly 22 through the through-hole 131. This embodiment protects the motor from overheating due to the current flowing to the coil 23 of the stator core assembly 22 under the high atmospheric temperature in the summer season and thus, defective operations are prevented. FIGURE 7 shows another embodiment of the motor apparatus according to the present invention. In the embodiment of FIGURE 7, the same components as the embodiments shown in FIGURES 2 and 5 are assigned the same reference numerals, and a detailed description of those parts has been omitted. On the crown of the annular depression 226 of a rotor 224, through-holes 231 are formed to circulate air in the space between the rotor 224 and the stator core assembly 22 to the outside. At the outside of each through-hole 231, a vane 232 is formed to suck air into the through-hole 231 during the rotation of the rotor 224. FIGURE 8 shows a plan view for illustrating the rotor 224 shown in FIGURE 7. On the crown of the annular depression 226 of the rotor 224, eight through-holes 231 are formed along the circumferential direction. At the outside of eight through-holes 231, eight vanes 232 are formed facing the rotating direction A of the rotor 224. FIGURE 9 shows a partial cross-sectional view of the portion around the through-hole 231 and the vane 232 at the line B-B in FIGURE 8. In FIGURE 9, an inclined surface 233 is provided facing the rotating direction A of each vane 232 so as to suck air into the through-hole 232 with the aid of the inclined surface 233 during the rotation of the rotor 224. According to the embodiment, the same effects as the embodiment shown in FIGURE 6 are obtained, and furthermore air is led into the through-holes 231 by the vanes 232, it is able to cool down the coil 23 of the stator core assembly 22 more efficiently than the embodiment shown in FIGURE 6. As described above, according to the present invention, it is possible to reduce the manufacturing cost of the motor apparatus, as the rotor can be rotated without a circuit board specifically designed for a rotating member. Furthermore, as it is possible to mount the stator and the main circuit board collectively at a time on the rotating member, the manufacturing cost of the motor apparatus can be reduced. In addition, as air in the space between the rotor and the stator can be circulated, it is also able to prevent the motor apparatus from being heated caused by the current flowing in the coil of the stator even under the state of high atmospheric temperature in the summer season and thus preventing defective operations or defects. As described above, the present invention can provide an extremely preferable cylinder motor apparatus and a magnetic recording or reproducing apparatus which utilizes such a cylinder motor apparatus.

Claims: A cylinder motor apparatus comprising: a chassis (11); a shaft (16); a main circuit board (31) fixed relative to the chassis (11) and having an electric circuit provided thereon to control the rotation of a rotor; a supporting member (13, 14, 17) for supporting the shaft (16) so as to be aligned at a predetermined angle from the normal to the plane of the circuit board on the chassis (11) in a freely rotatable state; a rotor (24) rotatable with the shaft (16), which rotor (24) has a depression (26) for receiving a stator defined therein and which rotor has a magnet (27) provided in said depression (26) for cooperation with the stator, the said depression (26) opening in a direction opposite from the supporting member (13, 14, 17); and a stator (22) housed in said depression (26), characterised in that the cylinder motor apparatus further comprises a cylindrical mounting member for mounting the stator (22) on the main circuit board (31) A cylinder motor apparatus as claimed in claim 1 wherein the supporting member comprises the stationary cylinder (14) of the cylinder motor apparatus. A cylinder motor apparatus as claimed in claim 2 wherein the stationary cylinder (14) is at a predetermined angle from the plane of the chassis (11). A cylinder motor apparatus as claimed in claim 3 wherein the circuit board (31) defines a through-hole (32) which is aligned at a predetermined angle from the rotating locus of the rotor (24) so that a part of the rotor (24) is rotatably supported in the through-hole (32). A cylinder motor apparatus as claimed in claim 4, further comprising, a rotating phase detecting sensor (29) provided on the circuit board (31) at a position opposite the through-hole (32) in relation to the stator (22). A cylinder motor apparatus as claimed in any preceding claim, wherein the stator housing (26) is annular and has an inner and an outer coaxial circular wall. A cylinder motor apparatus as claimed in claim 6 wherein a projection (30) extending from the inner wall of the stator housing extends further in the axial direction than the outer wall. A cylinder motor apparatus as claimed in one of claims 6 or 7 wherein the rotor (24) defines a through-hole (131) at the crown of the stator depression (26). A cylinder motor apparatus as claimed in claim 8, wherein the rotor (24) is provided with a vane (232) for directing air into the through-hole (131) of the rotor during the rotation of the rotor. A cylinder motor apparatus as claimed in any preceding claim further comprising: a rotary cylinder having a magnetic head, which is fixed to the shaft (16); a tape travel driving system adapted for driving a tape cassette loaded thereto, which includes a reel base, a capstan and a pinch roller; a tape guiding and supporting system provided to the chassis, which includes a tape pull-out member for pulling a tape out of the loaded tape cassette and making the tape contact with the stationary cylinder and the rotary cylinder; wherein an electric circuit controls the operation of the tape guiding and supporting system, and the recording or reproducing operation of information signals on or from the tape through the magnetic head. A recording and/or reproducing apparatus incorporating the cylinder motor apparatus as claimed in claim 10. A cylinder motor apparatus as defined in any preceding claim, comprising an electric circuit provided on the circuit board for controlling the rotation of the rotor.

Inventors: INUI MICHIO, KOBA AKINOBU, OHMURA SHUUJI, INUI, MICHIO, KOBA, AKINOBU, OHMURA, SHUUJI, INUI, MICHIO, C/O INTELLECTUAL DIV, TOSHIBA CORP, KOBA, AKINOBU, C/O INTELLECTUAL DIV, TOSHIBA CORP, OHMURA, SHUUJI, C/O INTELLECTUAL DIV, TOSHIBA CORP
Applicants: TOSHIBA AVE KK, TOSHIBA KK, KABUSHIKI KAISHA TOSHIBA, TOSHIBA AVE CO., LTD
Application year: 1994
Main classification: G11B5
IPC codes: G11B33, G11B25, G11B5, G11B15